1. Field of Invention
The present invention relates to an electro-optical device and an electronic apparatus using the electro-optical device.
2. Description of Related Art
There is a demand that electronic apparatuses, such as personal computers and portable devices, be smaller and thinner. It is very disadvantageous to use a large-scale light source having high directivity as a light source of a display device (electro-optical device) of such electronic apparatuses. Thus, such a light source is not actually used.
Therefore, for example, in a liquid crystal display device, a method is used in which light from a light source is guided to the back surface of a liquid crystal panel by a light guide member in order to illuminate the liquid crystal panel from the back surface thereof using, for example, a reflector plate, a diffusing plate, or a prism sheet.
However, related art display devices have the following problems.
For example, when the display device includes a transmissive liquid crystal panel or a transflective liquid crystal panel and a backlight (light source), a portion which does not pass the light is formed at, for example, a reflector plate (reflector electrode) or a drive circuit of the liquid crystal panel. Light which has returned after being emitted from the light source and reflected at the portion that does not pass light is absorbed by any one of the members, so that the light cannot be used. For this reason, the efficiency with which the light from the light source is used is low.
By using a prism sheet, the directivity of light can be increased. However, even if the directivity is increased, it is in a range of the order of xc2x130xc2x0 at most. Therefore, even if a micro-lens array is used, the light from the light source cannot be efficiently gathered at a light-transmissive window of the liquid crystal panel.
In particular, a transflective liquid crystal panel may be illuminated by light that passes a pin-hole shaped opening (light-transmissive window) formed in the reflector plate. In this case, the ratio of light reflected by the reflector plate with respect to incident outside light (hereinafter xe2x80x9cthe reflection ratioxe2x80x9d) and the ratio of light that passes through the opening with respect to light from the light source (hereinafter xe2x80x9cthe transmittance ratioxe2x80x9d) are each determined by the ratio between the area of the reflector plate and the area of its opening. Therefore, when the area of the opening is made to be large in order to increase the transmittance ratio, the area of the reflector plate becomes small, so that the reflectance ratio becomes small. On the contrary, when the area of the opening is made to be small to increase the reflectance ratio, the transmittance ratio becomes small (that is, they are in a trade-off relationship).
In this way, in related art display devices (electro-optical devices), light from the light source cannot be efficiently gathered at the light-transmissive window, so that the efficiency with which the light emitted from the light source is used is low.
An object of the present invention is to provide an electro-optical device which uses light emitted from a light source with high efficiency.
According to the present invention, the following exemplary electro-optical devices of (1) to (3) are described below.
(1) An electro-optical device includes a plurality of point light sources, a micro-lens array in which a plurality of micro-lenses are disposed, and a light modulation device including a plurality of light-transmissive windows. The electro-optical device is constructed so that light from the plurality of point light sources is focused at the light-transmissive windows by the micro-lens array.
(2) An electro-optical device includes a plurality of point light sources, a micro-lens array in which a plurality of micro-lenses are disposed, and a light modulation device including a plurality of light-transmissive windows. The point light sources, the micro-lenses of the micro-lens array, and the light-transmissive windows are disposed so that light from the plurality of point light sources is focused at the light-transmissive windows by the micro-lens array.
(3) An electro-optical device includes a plurality of point light sources, a micro-lens array in which a plurality of micro-lenses are disposed, and a light modulation device including a plurality of light-transmissive windows. The point light sources, the micro-lenses of the micro-lens array, and the light-transmissive windows are disposed so that the micro-lenses of the micro-lens array cause light from the plurality of point light sources to be focused at the plurality of light-transmissive windows.
Regarding each of the exemplary embodiments (1) to (3) of the invention, the following embodiments are, preferably, provided. However, the present invention is not limited to these embodiments.
(4) In an electro-optical device according to any one of the exemplary embodiments (1) to (3), where a pitch between the point light sources is Ps, a pitch between the light-transmissive windows is Pa, a pitch between the micro-lenses of the micro-lens array is PL, an optical distance between the point light sources and the micro-lens array is Ls, and an optical distance between the micro-lens array and the light-transmissive windows is La, the electro-optical device is constructed so that the following conditional expressions are satisfied:
PL={Psxc2x7Pa/(Ps+Pa)}xc2x7n (where n is a natural number)
La/Ls=Pa/Ps.
(5) In an electro-optical device according to any one of the exemplary embodiments (1) to (3), where a pitch between the point light sources is Ps, a pitch between the light-transmissive windows is Pa, a pitch between the micro-lenses of the micro-lens array is PL, an optical distance between the point light sources and the micro-lens array is Ls, and an optical distance between the micro-lens array and the light-transmissive windows is La, the electro-optical device is constructed so that the following conditional expressions are satisfied:
PL={Psxc2x7Pa/(Ps+Pa)}xc2x7n (where n is a natural number other than 2)
La/Ls=Pa/Ps.
(6) In an electro-optical device according to the aforementioned exemplary embodiments (4) or (5), the pitch Ps between the point light sources is greater than the pitch Pa between the light-transmissive windows.
(7) In an electro-optical device according to the aforementioned exemplary embodiments (4) or (5), the pitch Ps between the point light sources is equal to the pitch Pa between the light-transmissive windows.
(8) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (7), the pitch between the point light sources is, in a state where the micro-lens array is not provided, set so that a quantity of the light from the plurality of point light sources in a plane which passes through each light-transmissive window becomes substantially uniform.
(9) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (7), in a state where the micro-lens array is not provided, where a standard deviation in a distribution of a quantity of the light from each point light source in a plane which passes through each light-transmissive window is "sgr", the pitch between the point light sources is equal to or less than 2.3"sgr".
(10) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (7), in a state where the micro-lens array is not provided, where a maximum value and a minimum value of a quantity of the light from the plurality of point light sources in a plane which passes through each light-transmissive window are a and b, respectively, the pitch between the point light sources is set so that a light quantity ratio b/a is equal to or greater than 0.9.
(11) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (10), the electro-optical device is constructed so that the light from the point light sources is used to form an image in a/the plane which passes through each light-transmissive window, and so that an area of a portion where an image of each point light source in the plane and each light-transmissive window overlap does not change to the extent possible even when the image of each point light source and each light-transmissive window are displaced relative to each other.
(12) An electro-optical device according to the aforementioned exemplary embodiment (11), the electro-optical device is constructed so that the area of each portion where the image of each point light source in the plane and each light-transmissive window overlap does not change to the extent possible even when the image of each point source and each light-transmissive window are displaced relative to each other in a first direction and/or a second direction perpendicular to the first direction in the plane.
(13) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (12), the electro-optical device is constructed so that the light from the point light sources is used to form an/the image in a/the plane which passes through each light-transmissive window, and so that an/the image of each point light source in the plane is included in each light-transmissive window.
(14) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (12), the electro-optical device is constructed so that the light from the point light sources is used to form an/the image in a/the plane which passes through each light-transmissive window, and so that each light-transmissive window is included in an/the image of each point light source in the plane.
(15) In an electro-optical device according to the aforementioned exemplary embodiments (13) or (14), a difference between a length in a first direction of the image of each point light source in the plane and a length in the first direction of each light-transmissive window, and a difference between a length in a/the second direction, which is perpendicular to the first direction, of the image of each point light source in the plane and a length in the second direction of each light-transmissive window is substantially equal to each other.
(16) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (12), the electro-optical device is constructed so that the light from the point light sources is used to form an image in a plane which passes through each light-transmissive window, and so that a length in a first direction of an image of each point light source in the plane is greater than a length in the first direction of each light-transmissive window, and a length in a second direction, which is perpendicular to the first direction, of the image of each point light source in the plane is less than a length in the second direction of each light-transmissive window.
(17) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (12), the electro-optical device is constructed so that the light from the point light sources is used to form an image in a plane which passes through each light-transmissive window, and so that, in a first direction in the plane, each light-transmissive window is included in an image of each point light source in the plane, and, in a second direction which is perpendicular to the first direction in the plane, the image of each point light source in the plane is included in each light-transmissive window.
(18) In an electro-optical device according to the aforementioned exemplary embodiments (16) or (17), a contour of an image of each point light source in the plane includes a pair of straight-line portions that are substantially parallel to the first direction.
(19) In an electro-optical device according to any one of the aforementioned exemplary embodiments (16) to (18), a contour of each light-transmissive window includes a pair of straight-line portions that are substantially parallel to the second direction.
(20) In an electro-optical device according to any one of the aforementioned exemplary embodiments (11) to (19), a shape of each light-transmissive window is a substantially square shape or a substantially rectangular shape, and a shape of an image of each point light source in the plane is a substantially square shape or a substantially rectangular shape.
(21) In an electro-optical device according to the aforementioned exemplary embodiment (20), a predetermined side of each light-transmissive window and a predetermined side of an image of each point light source in the plane is substantially parallel to each other.
(22) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (21), the micro-lens array is a micro Fresnel""s lens array.
(23) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (22), the micro-lens array is formed by injection molding or photopolymerization.
(24) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (23), the light modulation device is a transmissive liquid crystal panel or a transflective liquid crystal panel.
(25) In an electro-optical device according to any one of the aforementioned exemplary embodiments (1) to (23), the light modulation device is a transflective liquid crystal panel.